The present invention relates, in general, to semiconductor structures for use in optical devices which include a silicon substrate having a near lattice matched semiconductor crystal deposited thereon containing a direct bandgap quantum well or an indirect bandgap quantum well with an isoelectronic impurity to form an isoelectronic center (IEC).
Recently, there has been tremendous interest in monolithically integrating optical devices with silicon devices. As silicon is an indirect bandgap material, it cannot be used as an efficient light source, until such time when a suitable IEC is incorporated into silicon allowing a reasonably efficient infrared light source. It is direct bandgap materials which can be used to manufacture very efficient lasers and light emitting diodes (LEDs). With the incorporation of IECs in some indirect bandgap materials, reasonably efficient LEDs have been fabricated. Recent improvements in epitaxial growth techniques have allowed the heteroepitaxy of semiconductor crystals such as GaAs, InP, GaP, ZnS, and others on silicon. GaAs and InP have a lattice mismatch of approximately 4% and 8%, respectively, with silicon. GaP and ZnS, however, have lattice mismatches with silicon which are very small (less than 0.4%), and can be referred to as near lattice matched crystals on silicon. Use of these near lattice matched crystals on silicon prevents formation of large numbers of misfit dislocations.